In the stitchless binding of a book it is necessary to apply to the edge of the stack of leaves or pages an adhesive so as to saturate the very edge of every page and form a sturdy back to which a cover sheet is applied. It is essential that every sheet have its back edge anchored in the layer of glue or adhesive applied to the back of the stack; if any one sheet is not anchored and falls out the book is unsalable.
Such an operation is usually carried out in a three-part machine having an assembly station, a gluing station downstream therefrom, and a drying or setting station. A carriage adapted to clamp the stack of sheets is displaceable between these stations. In use the bookbinder fits a stack of sheets into the carriage at the assembly station and then displaces it over a glue-coated roller at the gluing station and allows the freshly glued stack to sit in the drying station. A hot-melt adhesive is particularly useful in this type of arrangement so that the drying station need merely be equipped with a blower or the like to set and harden the adhesive by cooling it.
The principal problem with such a system is forming a stack wherein the back edges of all of the sheets are coplanar. In the prior art systems the upper surface of the carriage is perfectly horizontal and the one clamping element or plate against which the stack is pressed by the other clamping element is perfectly vertical. Thus the stack must be carefully arranged on this surface and then clamped in place. When a relatively thick stack of sheets is to be so positioned it is difficult to do this neatly. Furthermore in an arrangement wherein several such stacks must be placed, one after the other, in the clamp it is very difficult to achieve an adequately exact alignment of the back edges of the leaves.
Unless the leaves or sheets are perfectly aligned the conventional roller is unable to apply the needed uniform layer of glue to the stack edge. Any edge not absolutely in line with the edges of adjoining sheets would therefore not be appropriately coated. For these and other reasons the bookbinder using the apparatus must take particular care to tamp down and exactly align the leaves of each stack being glued.